This application claims the priority of German application 196 47 961.4, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a joining connection of an exhaust- gas-carrying pipe having a fastening flange and to a process for its manufacture.
A joining connection of this general type and a manufacturing process of this general type are known from German Patent Document DE 39 15 346 A1. For relieving the weld seam in the case of the connection described there, on the one hand, the pipe end to be inserted is expanded and then tapered, the pipe end assuming a wedge shape. On the other hand, a corresponding shape-equivalent sunk portion is created on the fastening flange so that, on the one hand, the pipe can be inserted in a simple manner into the flange by centering and, on the other hand, a press fit of the pipe in the flange can be achieved during the further insertion because of the wedge effect resulting from the shape of the pipe end. The described construction of the plug-in partners (flange--pipe) requires considerable manufacturing expenditures and is therefore very cost intensive. Furthermore, in the case of the known joining connection, an automation of the manufacture, which contains, for example, a welding robot, is virtually impossible because of the manufacturing tolerances of the pipe having an effect in the axial direction. In the case of each part to be joined, the welding robot always welds at the same point within the flange. If, in the plug-in position of the pipe, the pipe end is positioned deeper than desired in the flange, the robot will weld onto the interior side of the flange, whereby no weld joint is created between the pipe and the flange.
If the pipe end is positioned higher than desired in the flange, the robot will weld onto the flange which also does not result in a weld joint of the plug-in partners. Between these extreme relative positions, many axial positions of the pipe end with respect to the flange are possible which, however, permit only very unsatisfactory, that is, qualitatively poor weld joints. Because of the many possible position deviations, a welded connection in the optimal position does not occur frequently so that, in the case of an automated manufacturing, a high reject rate must be expected. This increases the costs of an automation since the costs of the quality control of the joint after its manufacturing reach significant figures.
It is an object of the invention to further develop a joining connection of the above-mentioned type or a process of the above-mentioned type for its manufacture in that an automation capability of the manufacture of the joining connection can be made possible which is simple and safe with respect to the process.
According to the invention, this object has been achieved by joining connection of at least one exhaust-gas-carrying pipe of an internal-combustion engine having a fastening flange which is inserted in its duct and, on its opening edge situated inside the duct, is welded to the duct wall of the flange, characterized in that, on the duct wall, at least one support projection which projects radially inward into the duct is constructed in an axially position-defined manner with a plane support surface on which the pipe rests directly in the axial direction in the plug-in position, the interior wall of the pipe closing off flush with the end edge of the projection or projecting radially beyond it toward the inside.
According to the invention, this object has been achieved by process for manufacturing a joining connection according to claim 1, after the production of the flange and its duct, an exhaust-gas-carrying pipe being fitted in a positioning manner in the duct, and, on its opening edge situated in the duct, being welded to the duct wall, characterized in that, before the insertion of the pipe in the flange, inside the duct on the duct wall, at least one support projection, which projects into the duct in a radially inward manner, is produced in an axially position-defined fashion with a plane support surface, after which the pipe is inserted into the flange until its opening edge comes to rest on the support projection, during the production, the projection being constructed such that the inside wall of the pipe closes off flush with its interior end edge or projects beyond it toward the inside.
As the result of the invention, the support projection provides a stop for the exhaust gas pipe to be inserted which has an axially defined position. In mass production, all exhaust gas pipes therefore have the same position in the flange assigned to them independently of axial manufacturing tolerances. Because of the identical position, the welding robot, which is programmed with respect to a specific point in the flange, specifically the area of the contact of the pipe on the supporting projection, can generate a weld joint of high durability which is the same for all assembly components. Because of the identical position, the robot will always weld at the position which is correct for an optimal weld joint. The support projection can be mounted on the flange in a simple manner so that, on the whole, the manufacture of the desired joining connection can take place at very low expenditures. Special developments of the flange and the pipe, which, in addition, must even be adapted to one another, are eliminated. For obtaining a qualitatively satisfactory weld seam and thus a sufficient welded connection, it is absolutely necessary that, in the plug-in position of the two plug-in partners pipe and flange, the interior pipe side slightly projects beyond the end edge of the support projection toward the interior but at least closes off flush with it. As a result, the welding robot definitely reaches without any difficulty the point of the transition between the opening edge and the end edge of the support projection and can provide the weld seam (fillet weld) there. Because of the generating of a high-quality joining connection which is always successful during the manufacture, rejects of assembly components joined in a low-quality manner are prevented. This ensures the reliability of the process in the case of an automation of the manufacture of a joining connection.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.